The present invention relates to a pneumatic tire, more particularly to a unidirectional tread pattern suitable for running on dry pavements as well as snowy/icy pavements.
Heretofore, in order to improve steering stability on dry pavements, a widely employed technique is to increase the land ratio of the tread pattern as far as possible, in other words, to increase the tread pattern rigidity, namely, overall rigidity of tread elements such as block, rib and the like. However, if the land ratio becomes increased, since the volume of tread grooves is decreased, a shearing force of snow trodden and packed in the tread grooves decreases, and on-the-snow performance tends to deteriorate.
When the shearing force of the packed snow is large, it can produce a large traction force or braking force, therefore, good snow grip performance can be obtained.
On the other hand, in order improve steering stability on snowy/icy pavements, a widely employed technique is to increase the total length of the edges of the tread elements in the tread portion for example by forming sipes or cuts. This technique is commonly employed in winter tires so called studless tires.
If a large number of sipes is however, provided in the tread portion, the rigidity of the tread elements such as blocks is decreased, therefore, it is inevitable that the steering stability on dry pavements is deteriorated, and the tread portion suffers from uneven wear.